Progressive selection for neurovirulent genotypes in the brain of SIV-infected macaques.

OBJECTIVE: To compare the viral genotypes present in RNA from brain and peripheral blood mononuclear cells (PBMC) and DNA from brain during acute, asymptomatic and late stages of SIV infection of macaques. METHODS: Eighteen pigtailed macaques were intravenously inoculated with SIV. At 10, 21 and 56 days postinoculation, six were euthanized and the severity of encephalitis was assessed by microscopic examination. DNA and RNA were isolated from brain and PBMC, and the V1 region of env was amplified by the polymerase chain reaction and sequenced from over 800 different clones. RESULTS: Similar genotypes were detected in RNA from brain and PBMC at 10 days postinoculation, suggesting an unrestricted exchange of virus between the periphery and the brain during acute infection. There was a progressive increase in the percentage of neurovirulent genotypes in brain RNA from acute (14% of all genotypes detected in brain RNA) to early asymptomatic (45%), to late asymptomatic (52%) and to terminal (95%) infection. Fewer different genotypes were found in brain RNA than in PBMC RNA from macaques euthanized during early asymptomatic (2.5 and 5 different genotypes, respectively; P = 0.007), late asymptomatic (2 and 5 different genotypes, respectively; P = 0.003) and terminal (2 and 4 different genotypes, respectively; P < 0.001) infection. CONCLUSION: These data demonstrate that the almost exclusive replication of neurovirulent genotypes in the brain seen at late-stage infection is a progressive process that begins early in infection and continues to late stage disease.

Neuroprotective and anti-human immunodeficiency virus activity of minocycline.

CONTEXT: The prevalence of human immunodeficiency virus (HIV) central nervous system (CNS) disease has not decreased despite highly active antiretroviral therapy. Current antiretroviral drugs are expensive, have significant adverse effects including neurotoxicity, and few cross the blood-brain barrier. OBJECTIVE: To examine the ability of minocycline, an antibiotic with potent anti-inflammatory and neuroprotective properties, to protect against encephalitis and neurodegeneration using a rapid, high viral load simian immunodeficiency virus (SIV) model of HIV-associated CNS disease that constitutes a rigorous in vivo test for potential therapeutics. DESIGN AND SUBJECTS: Five SIV-infected pigtailed macaques were treated with 4 mg/kg per day of minocycline beginning at early asymptomatic infection (21 days after inoculation). Another 6 macaques were inoculated with SIV but remained untreated. Blood and cerebrospinal fluid (CSF) samples were taken on days 7, 10, 14, 21, 28, 35, 43, 56, 70, 77, and 84, and all macaques were humanely killed at 84 days after inoculation, a time that corresponds to late-stage infection in HIV-infected individuals. MAIN OUTCOME MEASURES: Blood and CSF samples were tested for viral load by real-time reverse transcription-polymerase chain reaction and levels of monocyte chemoattractant protein 1 were quantitated by enzyme-linked immunosorbent assay. The presence and severity of encephalitis was determined by microscopic examination of tissues. Central nervous system inflammation was further assessed by measuring infiltration and activation of macrophages, activation of p38 mitogen-activated protein kinase and expression of amyloid precursor protein by quantitative immunohistochemistry. RESULTS: Minocycline-treated macaques had less severe encephalitis (P = .02), reduced CNS expression of neuroinflammatory markers (major histocompatibility complex class II, P = .03; macrophage marker CD68 , P = .07; T-cell intracytoplasmic antigen 1, P = .03; CSF monocyte chemoattractant protein 1, P = .001), reduced activation of p38 mitogen-activated protein kinase (P<.001), less axonal degeneration (beta-amyloid precursor protein, P = .03), and lower CNS virus replication (viral RNA, P = .04; viral antigen, P = .04). In in vitro analysis, minocycline suppression of HIV and SIV replication in cultured primary macrophages did not correlate with suppression of activation of p38-mitogen-activated protein kinase pathways, whereas suppression in primary lymphocytes correlated with suppression of p38 activation. CONCLUSIONS: In this experimental SIV model of HIV CNS disease, minocycline reduced the severity of encephalitis, suppressed viral load in the brain, and decreased the expression of CNS inflammatory markers. In vitro, minocycline inhibited SIV and HIV replication. These findings suggest that minocycline, a safe, inexpensive, and readily available antibiotic should be investigated as an anti-HIV therapeutic.

Dysregulation of mitogen-activated protein kinase signaling pathways in simian immunodeficiency virus encephalitis.

Central nervous system (CNS) disease is a frequent complication of human immunodeficiency virus (HIV)-1 infection. Identification of cellular mechanisms that control virus replication and that mediate development of HIV-associated neuropathology will provide novel strategies for therapeutic intervention. The milieu of the CNS during HIV infection is extraordinarily complex because of infiltration of inflammatory cells and production of chemokines, cytokines, and neurotoxic molecules. Cells in the CNS must integrate signaling pathways activated simultaneously by products of virus replication and infiltrating immune cells. In this study, we examined activation of mitogen-activated protein kinases (MAPKs) in the CNS of simian immunodeficiency virus-infected macaques during acute, asymptomatic, and terminal infection. We demonstrate that significantly increased (P < 0.02) activation of ERK MAPK, typically associated with anti-apoptotic and neuroprotective pathways, occurs predominantly in astrocytes and immediately precedes suppression of virus replication and macrophage activation that occur after acute infection. In contrast, significantly increased activation of proapoptotic, neurodegenerative MAPKs JNK (P = 0.03; predominantly in macrophages/microglia), and p38 (P = 0.03; predominantly in neurons and astrocytes) after acute infection correlates with subsequent resurgent virus replication and development of neurological lesions. This shift from classically neuroprotective to neurodegenerative MAPK pathways suggests that agents that inhibit activation of JNK/p38 may be protective against HIV-associated CNS disease.